Discovering proximate apparatus and services in a wireless network

ABSTRACT

A searching apparatus is put into the position of identifying the available apparatuses and services in its proximity in that an apparatus to be discovered periodically separates itself from its Access Point and builds up its own Ad hoc Network (AHN) which can be recognized via its Service Set Identifier (SSID) by the searching apparatus.

The invention relates to a method of enabling apparatuses in a wirelessnetwork (wireless LAN, WLAN) to discover other apparatuses and servicesin their proximity.

Wireless networks in spatially bounded areas (referred to as local areanetworks, LAN) are used within very wide fields. A field of applicationis, for example, computer-LAN in which a plurality of computers and aplurality of peripheral apparatuses such as printers, scanners,projectors, etc. are combined. These LANs are widely used in, forexample, companies. They usually have a plurality of Access Points (AP)via which a user can connect to a portable WLAN-capable apparatus in thenetwork and can thus use, for example, the company's main framecomputer. Moreover, the use of generally available peripheralapparatuses such as printers, scanners, UHP projectors, etc. is madepossible in that they are also connected to the network and can beaccessed by several users. This provides the possibility of, forexample, the fixed installation of the peripheral apparatuses inconference rooms, in which a lecturer or speaker only needs to connecthis laptop to the network for communication with the peripheralapparatus.

This poses the problem that the apparatus which is in closest proximitymust be occasionally selected from a plurality of equivalentapparatuses. For example, when a user with a laptop searches a printerin a building which is unknown to him, he is interested in finding theprinter which is in closest proximity to his current location, ratherthan a printer which may be present in another building or on anotherfloor.

The current Discovery Frameworks such as, for example, UniversalPlug&Play (UPnP) provide the possibility of discovering apparatuses andservices which can be reached via the network or are available in thenetwork. However, in the current state of the art, it is not possible tolimit the discovery of apparatuses and services to locally proximateapparatuses and services.

A search by means of Universal Plug&Play (UPnP) will thus find allappropriate apparatuses and services which are present in the samenetwork. Consequently, the number of discovered apparatuses may berelatively large, dependent on the WLAN size. Without furtherinformation about the distance between the apparatuses discovered bymeans of Universal Plug&Play (UPnP), the user cannot know whichapparatuses are spatially most proximate to him.

The network with which a WLAN-capable apparatus is connected usuallyconsists of a plurality of Basic Service Sets (BSSs) which areinterconnected by a distribution system (DS). Each Access Point (AP) andthe apparatuses connected thereto constitute a Basic Service Set (BSS).An apparatus connected to an Access Point (AP) can query a list ofdifferent available Service Sets (SSs) within the range of its WLANtransceiver (about 100 meters), without separating itself from the AP.The list states a series of Access Points (as BSSs) and possibly Ad HocNetworks (independent BSSs). An apparatus can find out which networksare available, but it cannot find out which individual apparatuses arepart of the network. It is therefore impossible to discover the presenceof other apparatuses connected to an Access Point (AP). Even if thepresence of an apparatus were known, the user's local apparatus couldnot estimate the distance between the apparatus and the local user'sapparatus. An apparatus can only estimate the distance between itselfand a WLAN infrastructure by measuring the received signal strengths,but it cannot estimate the distance to other apparatuses.

It is an object of the present invention to provide a method with whichan apparatus can be put into the position of identifying the availableapparatuses and services in its proximity.

It was found that the distance between a WLAN-capable portable apparatusand other apparatuses and services, i.e. its relative position to themcan be determined and used when the apparatuses to be discovered in thelocal wireless network periodically build up their own Ad Hoc Networks.

It is an object of the present invention to provide a method ofdiscovering proximate apparatuses and services in a wireless networkwith at least one Access Point (AP), wherein an apparatus to bediscovered periodically separates itself from its Access Point andbuilds up its own Ad Hoc Network (AHN) which can be recognized via itsService Set Identifier (SSID) by a searching apparatus.

The method according to the invention enables a WLAN-capable apparatusconnected to an Access Point to discover and identify other proximateapparatuses and their services. In this way, new proximity-basedapplications become possible. Moreover, the method according to theinvention has the advantage that the infrastructure of the WLAN does notneed to be changed. The method according to the invention is directlyapplicable for use with available apparatuses because the WLANtechnology is already widely used.

The method according to the invention is particularly suitable when auser having a wireless mobile apparatus would like to discover and useservices in his proximity. Examples of such services are printer,projector, music player and imaging services.

Both the mobile apparatus of the user (hereinafter also referred to as“searching apparatus”) and the apparatuses providing services(hereinafter also referred to as “apparatuses to be discovered”) areconnected to at least one WLAN Access Points so that they cancommunicate with each other.

Dependent on the output, the range covered by an Access Point may vary.Ranges of about 100 meters are achieved in buildings when using theconventional full power output. A plurality of Access Points may beinterconnected to one large wireless network via a distribution systemso as to cover, for example, a building completely.

In the method according to the invention, the searching apparatusinitially discovers all those apparatuses to be discovered that are inits proximity. When at least one other apparatus is discovered in theproximity of the searching apparatus, the search for services in theapparatuses that have been found can be performed in a second step ofthe method according to the invention, as described below.

According to the invention, to be discoverable for the searchingapparatus, the apparatuses to be discovered separate themselvesperiodically from their Access Point for a short period of time andbuild up their own Ad Hoc Network. This Ad Hoc Network can then be foundby apparatuses other than the searching apparatus. Dependent on thepower output of the WLAN cards, the range covered by such an Ad HocNetwork may vary. At the current, customary full power output, ranges ofabout 100 meters are achieved in buildings. In the preferred variant ofthe method according to the invention, the Ad Hoc Network (AHN) does notcomprise any other elements, apart from the apparatus it has generated.

In this way, a plurality of mutually independent Ad Hoc Networks isbuilt up periodically within a WLAN, dependent on the number ofapparatuses to be discovered, all of which Ad Hoc Networks comprise onlyone element, namely the apparatus that is to be discovered. Whengenerating its own Ad Hoc Network, the apparatus supplies itsidentification name so as to be unambiguously identifiable. To this end,the Service Set Identifier (SSID) of the Ad Hoc Network (AHN) includesan unambiguous identification name of the apparatus (UUID) in thepreferred method according to the invention.

The Service Set Identifier (SSID) of the Ad Hoc Network (AHN) providedby the apparatus to be discovered should be different from the SSID ofthe Access Points, which can be effected, for example, by means of aprefix and/or a suffix. In this way, the relevant SSID can beunambiguously assigned to an apparatus. A searching apparatus (forexample, a user's Notebook) can now periodically retrieve the list ofvisible SSIDs from its WLAN transceiver. When an apparatus to bediscovered (for example, a UHP projector) has made itself discoverablefor the searching apparatus in the manner described hereinbefore, theSSID of the apparatus to be discovered appears on this list.

The classification of the different discovered apparatuses as toproximity or remoteness is made possible by means of the methodaccording to the invention in that the searching apparatus queries, viaits WLAN transceiver, the signal strength of the apparatuses that havebeen found. This information is available because every apparatus thathas been found is observed as an independent Ad Hoc Network. The higherthe signal strength for an apparatus that has been found, the closer itis situated to the searching apparatus. In a preferred method accordingto the invention, the searching apparatus classifies the apparatusesthat have been found with a signal strength of more than −60 dBm asproximate apparatuses. In a second variant, the searching apparatusclassifies the apparatuses that have been found in accordance with theirremoteness so that the list thereby produced, or the upper segment ofthe list, can be indicated to the user.

The method according to the invention will be elucidated with referenceto FIG. 1.

FIG. 1 shows an arrangement of apparatuses for performing the methodaccording to the invention for discovering proximate apparatuses andservices in a wireless network.

As is shown in FIG. 1, a proximate apparatus 2 to be discovered and aremote apparatus to be discovered are connected to an Access Point (AP)1 and periodically separate themselves from this Access Point so as tobuild up their own Ad Hoc Network. A searching apparatus 4 searchingservices in its close proximity (for example with a radius of 10 meters)receives a list of SSIDs with the associated signal strengths. If theAccess Point 1 has a signal strength of, for example, −32 dBm, −37 dBmfor the apparatus 2 and −65 dBm for the apparatus 3, the searchingapparatus 1 can identify apparatus 2 as a proximate apparatus withreference to these signal strengths.

In the manner described hereinbefore, the user of the searchingapparatus acquires a list of those apparatuses to be discovered that arein his proximity. To find out whether a service desired by the user isavailable in his proximity, the method according to the invention can beperformed in such a way that, by means of a Discovery Framework,preferably by means of Universal Plug&Play (UPnP), the searchingapparatus is capable of accessing the services of the apparatus to bediscovered.

In this variant of the method, the searching apparatus starts a UPnPsearch by means of the discovered UUID after it has discovered at leastone apparatus in its proximity. UPNP ensures that the searchingapparatus finds and can use the services offered by the other apparatus.The user can then be informed about appropriate services in itsproximity.

In the preferred method according to the invention, the searchingapparatus finds, by means of a Universal Plug&Play (UPnP) search amongthe proximate apparatuses, that apparatus which provides the desiredservice.

The method described hereinbefore, by which a searching apparatusidentifies apparatuses to be discovered and estimates their distance canalso be performed after a UPnP search. First, all desired services thatare available in the network are discovered by means of UPnP andsubsequently it is determined which services are in the user'sproximity.

Accordingly, methods according to the invention in which the searchingapparatus initially discovers all desired services available in thenetwork by means of UPnP and subsequently determines which services arein its proximity, are also preferred.

According to the invention, an apparatus to be discovered separatesitself periodically from its Access Point for a short period of time soas to build up its own Ad Hoc Network. To prevent disturbances andpossibly active communication between the apparatuses to be discovered,the periods of time in which the apparatus to be discovered is separatedfrom its Access Point should be short. In this case, methods accordingto the invention are preferred wherein the period of time in which theapparatus to be discovered is separated from its Access Point ismaximally 1 s, preferably maximally 100 ms, particularly preferablymaximally 50 ms and particularly maximally 10 ms.

The more frequently an apparatus to be discovered separates itself fromits Access Point so as to build up its own Ad Hoc Network, the faster itcan be found by searching apparatuses because they do not need to waittoo long for an update of the SSID list. In the preferred methodaccording to the invention, the repetition frequency of separation ofthe apparatus to be discovered from its Access Point is 0.5 to 100 Hz,preferably 2 to 80 Hz, particularly preferably 5 to 60 Hz andparticularly 10 to 50 Hz.

List of Reference Numerals

-   1 Access Point (AP)-   2 proximate apparatus to be discovered-   3 remote apparatus to be discovered-   4 searching apparatus

1. A method of discovering proximate apparatuses and services in awireless network with at least one Access Point (AP), wherein anapparatus to be discovered periodically separates itself from its AccessPoint and builds up its own Ad Hoc Network (AHN) which can be recognizedvia its Service Set Identifier (SSID) by a searching apparatus.
 2. Amethod as claimed in claim 1, wherein the Ad Hoc Network (AHN) does notcomprise any further elements apart from the apparatus it has generated.3. A method as claimed in claim 1, wherein the Service Set Identifier(SSID) of the Ad Hoc Network (AHN) includes an unambiguousidentification name of the apparatus (UUID).
 4. A method as claimed inclaim 1, wherein the searching apparatus queries, via its WLANtransceiver, the signal strength of the apparatuses that have beenfound.
 5. A method as claimed in claim 4, wherein the searchingapparatus classifies the apparatuses that have been found with a signalstrength of more than −60 dBm as proximate apparatuses.
 6. A method asclaimed in claim 1, wherein, by means of a Discovery Framework,preferably by means of Universal Plug&Play (UPnP), the searchingapparatus is capable of accessing, the services of the apparatus to bediscovered.
 7. A method as claimed in claim 6, wherein, by means of aUniversal Plug&Play (UPnP) search among the proximate apparatuses, thesearching apparatus finds that apparatus which provides the desiredservices.
 8. A method as claimed in claim 6, wherein the searchingapparatus initially discovers all desired services available in thenetwork by means of UPnP and subsequently determines which services arein its proximity.
 9. A method as claimed in claim 1, wherein the periodof time in which the apparatus to be discovered is separated from itsAccess Point is maximally 1 s, preferably maximally 100 ms, particularlypreferably maximally 50 ms and particularly maximally 10 ms.
 10. Amethod as claimed in claim 1, wherein the repetition frequency at whichthe apparatus to be discovered is separated from its Access Point is 0.5to 100 Hz, preferably 2 to 80 Hz, particularly preferably 5 to 60 Hz andparticularly 10 to 50 Hz.